Determination of the barakol content of mature leaves, young flowers of Senna siamea (Lam.) Irwin and Barneby and in the herbal recipes

Abstract

Barakol, a major substance from Senna siamea (Lam.) Irwin and Barneby, is found in variable amount depending upon the source of the plant. Scientific evidence to characterize the traditional preparation of S. siamea is needed. The aim of this study was to characterize the content of barakol in various plant sources and to validate the high-performance liquid chromatography (HPLC) method for the quantification of barakol content from plants harvested from five locations in the northeast of Thailand and in several herbal recipes in which S. siamea is one of the constituents. Barakol was extracted from fresh young leaves of S. siamea and identified by chromatographic and spectroscopic techniques. Barakol content in mature leaves and young flowers of S. siamea harvested from five northeastern provinces in Thailand and its content in herbal recipes were quantified by validated HPLC. Separation was performed using C18 column and gradient elution of ultrapure water and methanol. Three herbal recipes containing S. siamea were studied to select the suitable solvent with which to extract barakol. Barakol was verified and its content determined using a validated HPLC method with a good linearity (R 2 = 0.9999), accuracy (%recovery = 99.25 to 101.59%), and precision (%RSD < 2%) including limit of detection (LOD) and limit of quantitation (LOQ) (16.80 and 5.04 ng/mL, respectively). The average barakol content in mature S. siamea leaves and young flowers was 0.300 and 0.279% w/w, respectively. Boiling water extracts yielded the highest barakol content in three herbal recipes (0.077, 0.123, and 0.085% w/w). Boiling water was an appropriate solvent to maximize barakol yield from herbal recipes containing S. siamea from Surin mature leaves and Yasothorn young flowers.